Designer and marketer of chips used in MP3 players plans to hire more engineers.By Kirk Ladendorf AMERICAN-STATESMAN STAFF Wednesday, April 21, 2004 A year ago, SigmaTel Inc. was pinching its pennies as it worked toward making a profit selling chips for portable MP3 music players. These days, the company, flush from proceeds from two public stock offerings, is solidly in the black and aiming to expand its engineering staff almost as quickly as it can find qualified candidates. "First you survive, and then you thrive," CEO Ron Edgerton said Tuesday. "We are thriving, and we expect to thrive even more...